Construction Of Amide Groupand C-H Direct Arylation Of Furan Catalyzed By NHC-Pd

The core of green chemistry is to reduce the environmental impact of chemical activities.it is a major concept that needs to be adhered during the development of chemistry.Therefore,it is of great significance to construct a target product by a non-toxic or less toxic coupling reaction.The amide structure is the basic building block of a living polypeptide.Amide compounds are widely found in nature and synthesis fields.As the directing group for the direct arylation reaction,the amide compound can be used as a substrate for various reactions directly.Therefore,the synthesis of amide groups has practical value.Using phenyl benzoate to prepare the target amide products is stable and inexpensive,not only reduces the reaction cost and environmental pollution,but also produce less corrosive halogen salt.In line with the concept of green chemistry,it is a new idea for the synthesis of amide compounds.The C-H direct arylation reaction can be used for the skeleton construction of aromatic ring with aromatic ring,or aromatic ring with heterocyclic ring.With a high atomic utilization rate and almost no by-products generated,it is a economical coupling reaction.In recent years,carbene palladium has been used in various coupling reactions including C-H direct arylation reaction,and has exhibited various advantages such as low Pd loading?high efficiency?stability and etc.The catalytic range of carbene palladium catalyst in C-H direct arylation reaction is wide.The catalytic substrate includes various heterocyclic substrates such as furans?thiophenes?oxazoles?thiazoles?imidazoles and pyrazoles.The benzene ring can also undergo directly arylation reaction under certain conditions.Carbene palladium precatalyst has great potential for development.In this paper,two carbene palladium catalyst will be synthesized and used in two reactions to further investigate the factors affecting the catalytic effect of carbene palladium complex.1.NHC-Pd complex C1 was synthesized,and its structure has been characterized by ~1HNMR,~1CNMR.The carboxylic acid phenol ester and aniline were used as raw materials to catalyze the C-N cross-coupling reaction.The effect of the skeleton on the catalytic efficiency of Pd complex was investigated,48 amide substrates were synthesized,and separated by GC,thin layer chromatography and characterized by NMR.2.The bukly hindered NHC-Pd precatalysts K3 was synthesized,the C-H direct arylation reaction of various furan compounds such as2-methylfuran,2-pentylfuran,benzofuran and furfural was carried under mild reaction conditions.Multiple furan products were synthesized and characterized.3.A variety of heterocyclic-type substrates such as thiophene,thiazole,oxazole,imidazole,pyrrole,pyridoimidazole,etc.were screened to extend the range of substrates to investigate the catalytic effect of large sterically hindered carbene palladium.The nitrofuran substrate was synthesized and used as a raw material to synthesize the furan drug dantrolene which is a skeletal muscle relaxant.